#include <stdio.h>
int main(){
	int n,i,count,total;
	while(scanf("%d",&n)!=EOF){
		count=0;
		total=0;
		while(n--){
			scanf("%d",&i);
			if(i<0){
				count+=i;
			}
			else
				count+=i/2;
			if(count<0)
				total++;
		}
		printf("%d\n",total);
	}
	return 0;
}